PLASMO: a simulation model for control of Plasmopara viticola on grapevine1

The problem of protecting grapevine against diseases is an old one, but in the last few years new techniques have been developed to reduce cost to the farmer and damage to the ecosystem. These are based on mathematical models describing the state of the plant-parasite environment system. A model for forecasting development of grapevine downy mildew (Plasmopara viticola) is presented. The input variables are temperature, rainfall and leaf wetness (determining infection by sporangia), and RH and temperature (for incubation period). The model also takes into account the limited survival of spores. The output is expressed as %, disease progress. Field validation tests, performed in 1990, 1991 and 1992 in several vineyards in Toscana (central Italy) showed a good correlation between observed and simulated infections. The model allowed the number of treatments to be reduced without any increase in downy mildew damage. It could in future be integrated with grapevine growth and development simulation models in an expert system to determine infected tissue area and thus the economic damage threshold.     

Application of fuzzy logic for the simulation of Plasmopara viticola using agrometeorological variables*

A mechanistic model called PLASMO was developed earlier to simulate grapevine downy mildew (Plasmopara viticola) and has been applied in several viticultural areas of Italy since 1988 by the collaboration of several research institutions of Firenze. In this study, a new simulation model based on fuzzy logic has been developed for the same structure (biological cycle of P. viticola). This approach allows classical quantitative information to be used together with qualitative information. Vague concepts can also be handled. Agrometeorological data is used, with an hourly time step, starting from budbreak to the end of the growing season. Air temperature, relative humidity, rainfall and leaf wetness are required. The simulated processes are the growth of grapevine leaf area and the main phases of the biological cycle of the pathogen: incubation, sporulation, germination, spore survival and inoculation. The main epidemiological outputs are timing of infection events and disease intensity. The performance of the model is evaluated and the mechanistic and fuzzy logic approaches are compared.     

Formation of satellite uredinia as an important trait related to grapevine colonization by Phakopsora meliosmae-myrianthae

Phakopsora meliosmae-myrianthae, the causal agent of Asian grapevine leaf rust, significantly reduces the photosynthetic efficiency of grapevine leaves in green symptomless tissues surrounding lesions. This study took a close look at grapevine leaf colonization kinetics by P. meliosmae-myrianthae and compared it to P. pachyrhizi–soybean and Uromyces appendiculatus–bean colonization. It is already known from the literature that soybean rust, similar to grapevine rust, has a negative effect on leaf photosynthesis greater than would be expected based on visual lesions. However, in contrast to soybean and grapevine rusts, the effect of bean rust on leaf photosynthesis is proportional to the diseased leaf area. Colonization progress was monitored by fungal biomass assessed via histological staining and quantitative polymerase chain reaction (qPCR). Individual lesions of P. meliosmae-myrianthae on grapevine, P. pachyrhizi on soybean and U. appendiculatus on common bean leaves were evaluated every 3–4 days, and the number of uredinia was counted. Staining showed that mycelial colonization did not extend beyond the lesion border. The number of P. pachyrhizi and P. meliosmae-myrianthae uredinia within the lesions increased over time (on average 14-fold), whereas the number of U. appendiculatus uredinia remained the same. These findings were corroborated by qPCR, which revealed a greater increase in fungal biomass for Phakopsora spp. than for U. appendiculatus until 12 days post-inoculation. The high number of satellite uredinia within lesions might be directly related to the impact of this pathogen in photosynthetic efficiency on symptomless areas of diseased grapevine leaves. This study identified accelerated formation of satellite uredinia as an important feature of grapevine colonization by P. meliosmae-myrianthae.     

Pathogenicity of <Emphasis Type="Italic">Mycochaetophora gentianae</Emphasis>, causal fungus of gentian brown leaf spot,as affected by host species,inoculum density,temperature, leaf wetness duration,and leaf position

When the influence of host species, inoculum density, temperature, leaf wetness duration, and leaf position on the incidence of gentian brown leaf spot caused by Mycochaetophora gentianae, was examined, the fungus severely infected all seven Gentiana triflora cultivars, but failed to infect two cultivars of G. scabra and an interspecific hybrid cultivar. Inoculum density correlated closely with disease incidence, and a minimum of 10² conidia/mL was enough to cause infection. In an analysis of variance, temperature and leaf wetness duration had a significant effect upon disease incidence, which increased with higher temperature (15–25°C) and longer duration of leaf wetness (36–72 h). No disease developed at temperatures lower than 10°C or when leaf wetness lasted <24 h. At 48-h leaf wetness, disease incidence was 0, 28, 77, and 85% at 10, 15, 20, and 25°C, respectively. Middle and lower leaves on the plant were more susceptible than upper leaves. In microscopic observations of inoculated leaves, >50% of conidia germinated at temperatures >15°C after 24-h leaf wetness. More appressoria formed at higher temperatures (15–25°C) with extended duration of leaf wetness (24–72 h). At 48-h leaf wetness, appressorium formation was 0, 8, 26, and 73% at 10, 15, 20, and 25°C, respectively. These results suggest that temperature and leaf wetness duration were important factors for infection of gentian leaves.     

Conidial production and viability of Calonectria pseudonaviculata on infected boxwood leaves as affected by temperature,wetness, and dryness periods

Calonectria pseudonaviculata causes lesions on boxwood leaves and twigs. Controlled-environment experiments were conducted to determine the effects of temperature and leaf wetness period on C. pseudonaviculata sporulation on diseased (cv. Suffruticosa) leaves and of dryness periods and high temperature on conidial survival. Infected leaves were incubated in moist chambers and subjected to six temperatures (9, 13, 17, 21, 25, and 29°C) and six leaf wetness periods (0, 12, 24, 40, 48, and 72 h). Spore production was influenced significantly by wetness period, temperature, and their interaction. Increasing duration of leaf wetness and increasing temperature generally increased sporulation, with no sporulation occurring at 29°C or 9 and 13°C, except at 72 h of wetness exposure, while it was optimal at 21°C. Detached leaves with profuse conidia were subjected to a range of drying (relative humidity at 65%) times (0, 2, 4, 6, and 8 h) at two temperatures of 21 and 29°C. Conidia were then harvested and plated on water agar. Germinating conidia were counted to measure the spore viability. Spore mortality increased with increasing dryness duration at both temperatures but occurred more quickly and severely at 29 than 21°C. Overall, this study extended biological knowledge of conditions required for crucial stages of the C. pseudonaviculata disease cycle and the obtained results will be vital for developing boxwood blight forecasting and management tools.     

Modelling the progress of Asiatic citrus canker on Tahiti lime in relation to temperature and leaf wetness

The combined effect of temperature (15°C, 20°C, 25°C, 30°C, 35°C, 40°C and 42°C) and leaf wetness duration (0, 4, 8 12, 16, 20 and 24 h) on infection and development of Asiatic citrus canker (Xanthomonas citri subsp. citri) on Tahiti lime plant was examined in growth chambers. No disease developed at 42°C and zero hours of leaf wetness. Periods of leaf wetness as short as 4 h were sufficient for citrus canker infection. However, a longer leaf duration wetness (24 h) did not result in much increase in the incidence of citrus canker, but led to twice the number of lesions and four times the disease severity. Temperature was the greatest factor influencing disease development. At optimum temperatures (25–35°C), there was 100% disease incidence. Maximum disease development was observed at 30–35°C, with up to a 12-fold increase in lesion density, a 10-fold increase in lesion size and a 60-fold increase in disease severity.     

Effects of Temperature and Wetness Duration on Infection of Oilseed Rape Leaves by Ascospores of Leptosphaeria maculans (Stem Canker)

In controlled environment experiments, ascospores of Leptosphaeria maculans (stem canker) infected oilseed rape (cv. Nickel) leaves and caused phoma leaf spots at temperatures from 8°C to 24°C and leaf wetness durations from 8 h to 72 h. The conditions that produced the greatest numbers of leaf spot lesions were a leaf wetness duration of 48 h at 20°C; numbers of lesions decreased with decreasing leaf wetness duration and increasing or decreasing temperature. At 20°C with 48 h of leaf wetness, it was estimated that one out of four spores infected leaves to cause a lesion whereas with 8 h of leaf wetness only one out of 300 spores caused a lesion. As temperature increased from 8°C to 20°C, the time from inoculation to the appearance of the first lesions (a measure of the incubation period) decreased from 15 to 5 days but leaf wetness duration affected the length of the incubation period only at sub-optimal temperatures. Analyses suggested that, within the optimal ranges, there was little effect of temperature or wetness duration on incubation period expressed as degree-days; the time until appearance of 50% of the lesions was ca. 145 degree-days. A linear regression of % leaves with lesions (P_l) (square-root transformed) on % plants with lesions (P_p) accounted for 93% of the variance: P_l=1.31+0.061P_p. This relationship was also investigated in winter oilseed rape field experiments in unsprayed plots from October to April in 1995/96 (cv. Envol), 1996/97 (cv. Envol), 1997/98 (cvs Bristol and Capitol) and 1998/99 (cvs Apex, Bristol and Capitol) seasons. The linear regression of % leaves with lesions (square-root transformed) on % plants with lesions accounted for 90% of the variance and had a similar slope to the controlled environment relationship: P_l=0.81+0.051P_p. These results were used to examine relationships between the development of phoma leaf spot on plants in winter oilseed rape crops, the incubation period of L. maculans and the occurrence of infection criteria (temperature, rainfall) in the autumns of 1996, 1997 and 1998.     

Pseudomonas syringae pv. syringae from cool climate Australian grapevine vineyards: new phylogroup PG02f associated with bacterial inflorescence rot

During the period 2006–2011, Pseudomonas syringae pv. syringae caused a bacterial inflorescence rot (BIR) epidemic in an Australian cool climate viticultural region. Molecular multilocus sequence typing of ‘housekeeping’ genes (MLST), biochemical testing and analysis of molecular variance (AMOVA) were used to characterize the genotypes and phenotypes of P. syringae pv. syringae grapevine isolates. Comparison of the MLST data with exemplars of phylogroups available at PAMDB demonstrated that the BIR isolates formed a new clade within P. syringae pv. syringae phylogroup 2 (PG02): putatively designated PG02f. Analysis of the MLST and phenotypic data by AMOVA demonstrated some genetic differences between the BIR isolates and the general vineyard P. syringae pv. syringae population. Isolates positive for syringopeptin, syringomycin and tyrosinase, tobacco leaf hypersensitivity reaction (HR), ampicillin resistance and grapevine leaf pathogenicity were genetically distinct from those negative for these factors. This study has shown that, generally, the core genome of P. syringae pv. syringae is only weakly associated with the virulence-associated traits. As the new phylogroup PG02f consists of the epidemic BIR isolates and nonpathogenic grapevine isolates, these genetically similar isolates differ greatly in pathogenicity and most of the other tested phenotypic traits. However, within the PG02f group, tobacco leaf HR and presence of sylC (the gene for phytotoxin syringolin A) are associated with the BIR and bacterial leaf spot (BLS) isolates, and negative for the nonpathogens, indicating that these two virulence factors may be associated with vineyard pathogenicity within the new Australian phylogroup.     

Stepped‐up surveillance for early detection of Anoplophora chinensis in a nursery district

The Plant Protection Service of Lombardy Region (Italy) has been working to control Anoplophora chinensis for many years. A specific plan was developed by the Plant Protection Service in 2011 to implement stepped‐up surveillance for early detection of this pest in the most important nursery area in the region. The Canneto sull'Oglio district area hosts the highest concentration of commercial nurseries in Lombardy. The nurseries specialize in the cultivation of full‐size deciduous ornamental trees. The reinforced surveillance plan includes the following steps: planning, inspection of the urban green spaces, surveillance in rural areas and surveillance of identified sources of risk. A new procedure was defined for the enhanced territorial surveillance, as there were no established guidelines to follow. Two buffer zones were delineated, with a 2 km radius and a 500 m radius around all the areas dedicated to nursery cultivation, and a grid of 500 × 500 m was superimposed on it. Between one and four inspection points were defined for each cell, depending on the risk to plant health, and more than 3450 inspection points were identified, corresponding to 11 233 potential host plants that were to be inspected. In addition, the fields of 16 nurseries classified as high risk sources were inspected as well as the potential hosts in the buffer zone of 100 m radius around them. The annual cost of the surveillance is 30 000 EUR, which corresponds to about 0.025% of the annual production value of the nurseries in this district.     

Effect of pea canopy architecture on microclimate and consequences on ascochyta blight infection under field conditions

In order to investigate the impact of pea canopy architecture and development on microclimate and infection by Mycosphaerella pinodes, two field experiments were conducted in 2009 and 2010 at Le Rheu (France) to obtain canopies contrasted in height, closure dynamic, leaf area index (LAI) and leaf area density (LAD). Three pea cultivars (Athos, Antares, Gregor) were sown at two (80 and 40 seeds/m² in 2009) and three densities (80, 40 and 30 seeds/m² in 2010) and microclimatic sensors were located inside the canopy (at the bottom and in the middle) and outside. Two main sources of wetness were identified: rainfall and dew. During rainfall periods, average daily leaf wetness duration (LWD) was about 15 h, and 3 to 10 h longer inside than outside the canopies. LWD was positively correlated with LAI until canopy closure during these periods. During dry periods when dew was the only source of leaf wetness, average daily LWD was short, decreasing as the canopy developed. Shorter LWDs were observed at the base than at the mid-level of the canopies and longer LWDs were observed outside the canopy and inside the less dense canopies irrespective of the cultivar. LWD was negatively correlated with canopy height and LAI during these periods. Slow wind speeds were recorded inside the canopies (less than 0.5 km/h) and no significant canopy effect was observed on air temperature. An infection model was developed and showed that only rainfall periods which induced long LWDs inside the canopy, were favourable to M. pinodes infection under our climatic conditions and suggested a more favourable microclimate inside dense canopies.     

Genetic structure and fungicide sensitivity of Botrytis cinerea populations isolated from grapevine in northern Italy

Grey mould, caused by Botrytis cinerea, is a disease severely affecting grape production in northern Italy. However, little information is available on the variability of B. cinerea populations associated with grapevine. The mode of reproduction, sensitivity to fungicides, and for the first time in Italy, the genetic structure of B. cinerea populations isolated from grapevine in a northern Italian region are reported. Botrytis cinerea isolates (317) were completely genotyped for six microsatellite loci and characterized for the presence of the transposable elements Boty and Flipper, for the mating type and for resistance to cyprodinil, fludioxonil, boscalid and fenhexamid. All the isolates were found to belong to B. cinerea Group II, indicating the absence of B. pseudocinerea in the investigated areas. The populations possess a high genotypic diversity, different frequencies of transposable elements and a mixed mode of reproduction. At a regional level, B. cinerea populations belong to a large and interconnected pathogen population that includes the major grape‐growing districts. The populations were generally sensitive to fungicides, with a low proportion (8%) of isolates resistant to cyprodinil, fludioxonil and boscalid. A small genetic distance was found between B. cinerea populations. However, the populations geographically isolated from the others by a mountain range showed a small but statistically significant genetic differentiation and a different pattern of fungicide resistance. The results show that northern Italian B. cinerea populations possess a high evolutionary potential and adaptive capacity.     

Endophytic Beauveria bassiana activates expression of defence genes in grapevine and prevents infections by grapevine downy mildew Plasmopara viticola

Fungal entomopathogens like Beauveria bassiana (Ascomycota: Hypocreales) are known as antagonists of insects with multiple functional and ecological roles, and have attracted increased attention as biocontrol agents in integrated pest management programmes. For some crop plants, it has been proven that endophytic B. bassiana, besides its entomopathogenic habit, can provide protection against plant pathogens or limit their damaging effects. However, for grapevine, limited knowledge is available on the influence of endophytic B. bassiana on fungal pathogens and about the mechanisms underlying putative protection effects. This study assessed the protective potential of endophytic B. bassiana against grapevine downy mildew Plasmopara viticola in greenhouse experiments. Three and seven days after a B. bassiana treatment, potted grapevine plants were inoculated with P. viticola and the evolving disease severity was assessed. Disease severity was significantly reduced in B. bassiana-treated plants compared to control plants, depending on the age of leaves. Furthermore, a microarray and an RT-qPCR analysis were performed to work out fundamental aspects of genes involved in the interaction between grapevine and B. bassiana. The results indicate an up-regulation of diverse defence-related genes in grapevine as a response to endophytic establishment of B. bassiana. Thus, endophytic establishment of an entomopathogenic fungus such as B. bassiana in grapevine plants would represent an alternative and sustainable plant protection strategy, with the potential for reducing pesticide applications in viticulture.     

Effects of inoculum density,leaf wetness duration and nitrate concentration on the occurrence of lettuce leaf spot

In Ehime Prefecture, Japan, lettuce leaf spot (Septoria lactucae) caused huge losses in marketable lettuce yields. To explore potential measures to control disease outbreaks, the effects of inoculum density, leaf wetness duration and nitrate concentration on the development of leaf spot on lettuce (Lactuca sativa) were evaluated. Conidia were collected from diseased plants in an infested field by single-spore isolation and were used to inoculate potted lettuce plants with different conidial concentrations. Lesions developed on inoculated lettuce plants at inoculum concentrations from 10⁰ to 10⁶ conidia/ml. The disease was more severe when the inoculum exceeded 10² conidia/ml, and severity increased with increasing concentrations. Assessment of the relationship between disease development and the duration of postinoculation leaf wetness revealed that symptoms appeared when the inoculated plants remained wet for 12 h or longer. The number of lesions and total nitrogen content in the lettuce leaves both increased when nitrate was applied.     

Influence of Environmental Conditions on Infection of Peach Shoots by Taphrina deformans

ABSTRACT The effect of weather conditions on the infection of peach shoots by Taphrina deformans was investigated both under orchard conditions and in controlled-environment experiments. Leaf curl incidence and severity were related to rainfall, length of wet periods, and temperature during wetness and during the incubation period, as well as to the development stage of shoots. Surface wetness was more important than rainfall for infection to occur. Minimum rainfall for infection was 3 mm, with a wet period of at least 12.5 h; higher amounts of rainfall did not cause infection when the wet period they triggered was shorter. Wet periods initiated by dew or fog were too short for infection to occur. Infection occurred only when air temperature was <16 degrees C during the wet period and <19 degrees C during incubation. Logistic equations relating relative disease incidence and either duration of wetness or temperature were developed under controlled-environment conditions, with asymptotes at >/=48 h of wetness and 相似文献   

Sensitivity to cymoxanil in populations of Plasmopara viticola in northern Italy

In 1993, control failures were reported on grapevine in northern Italy under severe downy mildew pressure after postinfection application of cymoxanil in mixtures with copper or mancozeb. A monitoring survey was started immediately in Piedmont (north-western Italy) in order to determine the sensitivity of populations of Plasmopara viticola to cymoxanil from those vineyards where the fungicide was not controlling the disease satisfactorily. In 1994 and 1995, monitoring surveys were extended to north-eastern Italy, where cymoxanil mixtures were not performing as well as in the past. Sampled populations were tested on detached leaf discs and on whole potted plants under controlled conditions. In 1993, 12 populations, sampled in Piedmont, showed MIC values (minimum inhibitory concentration) varying from 10 to more than 100 mg L⁻¹ cymoxanil. With a baseline reference population having a MIC value of 3 mg L⁻¹, resistance factors ranged from 3 to more than 30. In 1994, 17 populations out of 27 sampled in Trentino (north-eastern Italy) showed MIC values of 100 mg L⁻¹ or higher and in 1995, 32 populations out of 38 showed the same behaviour. In similar experiments, the MIC values of populations from nontreated plots were between 3 and 10 mg L⁻¹. In whole potted plant tests, populations with MIC values higher than 200 mg L⁻¹ in a leaf disc test were not controlled by 500 mg L⁻¹ of cymoxanil. The results of our study suggest that resistance to cymoxanil in P. viticola may contribute to a lack of disease control in Italian vineyards.     

Infection of Linseed by Alternaria linicola; Effects of Inoculum Density, Temperature, Leaf Wetness and Light Regime

Controlled environment studies were conducted to determine the effects of inoculum density, temperature, leaf wetness and light regime on the infection of linseed by Alternaria linicola. The % cotyledons and leaves with symptoms, and the disease severity (% leaf area with symptoms) increased linearly when the inoculum density increased from 1×10³ to 1×10⁵ conidiaml^–1. The first symptoms appeared on cotyledons and leaves 4 and 6 days after inoculation, respectively. Eight hours of leaf wetness were sufficient to initiate the disease at 25°C but not at 15°C, when 10-h periods of leaf wetness were required. % leaf area with symptoms was lower at 15°C than that at 25°C irrespective of the leaf wetness periods tested. Interruption of a continuous leaf wetness period by a 12-h dry period, occurring at any time between 1 and 18h after inoculation, decreased the % cotyledons with symptoms and the disease severity, with the greatest reductions (60% and 100%, respectively) being observed when the dry period began 6h after inoculation. A. linicola conidia were able to exploit successive 12-h periods of leaf wetness cumulatively to infect linseed plants. Disease incidence and severity were positively correlated with the dark period following inoculation, but they were negatively related to the length of the initial light period. Our findings suggest that infection of linseed by A. linicola and further development of symptoms can occur under unfavourable environmental conditions.     

Identification of grapevine marker genes for early,non‐destructive Eutypa lata infection diagnosis

Eutypa lata is the causal agent of eutypa dieback, a highly damaging trunk disease affecting all grape‐growing areas, with currently neither an efficient curative treatment nor an early non‐destructive diagnostic method. The present work was carried out to discover grapevine genes expressed in response to the presence of E. lata that could be useful to develop an early (before visible foliar symptoms) and non‐destructive (using grapevine leaves) diagnostic tool. Microarray analyses were carried out from (i) infected plants showing characteristic E. lata foliar and vascular symptoms and positive pathogen recovery from vascular lesions (S⁺R⁺), (ii) infected plants showing no symptoms (S^?R⁺), and (iii) symptomless plants with negative pathogen recovery (S^?R^?). Vineyard and greenhouse‐grown plants, naturally or artificially infected respectively, and uninoculated controls were characterized and leaf RNA was hybridized with 15k operon grapevine oligonucleotide microarrays. Among the grapevine genes differentially expressed between S^?R⁺ and S^?R^? plants in greenhouse and vineyard conditions, 10 were highlighted as robust candidate genes for diagnosis: seven were specifically involved in response to infection and three were associated with symptom absence. Five were confirmed to be effective diagnostic marker genes usable in a qRT‐PCR‐based test performed on RNA extracted from grapevine leaves cultivated in either greenhouse or vineyard conditions. Furthermore, their expression profiles in response to infection with E. lata or other major grapevine fungi (Erysiphe necator, Plasmopara viticola, Botrytis cinerea) could be distinguished. The usefulness of these genes to develop an early and non‐destructive method for diagnosis of E. lata infection is discussed with regard to the advantages and drawbacks of previous E. lata diagnostic studies.     

Effect of temperature,relative humidity,leaf wetness and leaf age on <Emphasis Type="Italic">Spilocaea oleagina</Emphasis> conidium germination on olive leaves

The effects of temperature, relative humidity (RH), leaf wetness and leaf age on conidium germination were investigated for Spilocaea oleagina, the causal organism of olive leaf spot. Detached leaves of five ages (2, 4, 6, 8 and 10 weeks after emergence), six different temperatures (5, 10, 15, 20, 25 and 30°C), eight wetness periods (0, 6, 9, 12, 18, 24, 36 and 48 h), and three RH levels (60, 80 and 100%) were tested. Results showed that percentage germination decreased linearly in proportion to leaf age (P < 0.001), being 58% at 2 weeks and 35% at 10 weeks. A polynomial equation with linear term of leaf age was developed to describe the effect of leaf age on conidium germination. Temperature significantly (P < 0.001) affected frequencies of conidium germination on wet leaves held at 100% RH, with the effective range being 5 to 25°C. The percent germination was 16.1, 23.9, 38.8, 47.8 and 35.5% germination at 5, 10, 15, 20 and 25°C, respectively, after 24 h. Polynomial models adequately described the frequencies of conidium germination at these conditions over the wetness periods. The rate of germ tube elongation followed a similar trend, except that the optimum was 15°C, with final mean lengths of 175, 228, 248, 215 and 135 μm at 5, 10, 15, 20 and 25°C, respectively after 168 h. Polynomial models satisfactorily described the relationships between temperature and germ tube elongation. Formation of appressoria, when found, occurred 6 h after the first signs of germination. The percentage of germlings with appressoria increased with increasing temperature to a maximum of 43% at 15°C, with no appressoria formed at 25°C after 48 h of incubation. Increasing wetness duration caused increasing numbers of conidia to germinate at all temperatures tested (5–25°C). The minimum leaf wetness periods required for germination at 5, 10, 15, 20 and 25°C were 24, 12, 9, 9 and 12 h, respectively. At 20°C, a shorter wetness period (6 h) was sufficient if germinating conidia were then placed in 100% RH, but not at 80 or 60%. However, no conidia germinated without free water even after 48 h of incubation at 20°C and 100% RH. The models developed in this study should be validated under field conditions. They could be developed into a forecasting component of an integrated system for the control of olive leaf spot.